Commutation Control Method and Device for Brushless Direct Current Motor, and Storage Medium

ABSTRACT

A commutation control method, a device for a brushless direct current motor, and a storage medium are described. The method includes performing detection on a position of a rotor in a brushless direct current motor. The detection is further configured to be triggered by commutation of the brushless direct current motor. The method includes determining, for the brushless direct current motor, a first drive scheme corresponding to the detected position of the rotor, the first drive scheme indicates a manner in which a three-phase full-bridge circuit of the brushless direct current motor operates; updating a pulse width modulation (PWM) drive signal, the updating is performed on the basis of the first drive scheme; and using the updated PWM drive signal to control the brushless direct current motor to perform commutation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT International Application No.PCT/CN2019/098114, filed Jul. 29, 2019 entitled “Commutation ControlMethod And Device For Brushless Direct Current Motor, and StorageMedium,” the entire content of which is incorporated herein byreference.

TECHNICAL FIELD

The disclosure relates to the technical field of motor control, and inparticular to a commutation control method and device for a Brush LessDirect Current Motor (BLDCM), and a storage medium.

BACKGROUND

Currently, a high-speed miniaturized BLDCM is more and more widely used,especially in a field of a small electric tool such as a hand-heldvacuum cleaner, or the like.

As shown in FIG. 1, in the related art, a three-phase six-state PulseWidth Modulation (PWM) drive signal is usually acted to a three-phasefull-bridge circuit, to control on and off of a corresponding bridge armswitching device in the three-phase full-bridge circuit, therebyimplementing commutation control for the BLDCM.

However, in a practical application, the PWM drive signal may not beable to control the BLDCM to perform commutation in time.

SUMMARY

In order to solve the problem in the related art, embodiments of thedisclosure proposes a commutation control method and device for a BLDCM,and a storage medium, which is capable of implementing a timelycommutation for the BLDCM.

Embodiments of the disclosure provide a commutation control method for aBLDCM, which includes the following operations.

A position of a rotor in the BLDCM is detected, here the detecting isfurther configured to be triggered by commutation of the BLDCM.

A first drive scheme, corresponding to the detected position of therotor, of the BLDCM is determined, here the first drive scheme indicatesa manner in which a three-phase full-bridge circuit of the BLDCMoperates.

A PWM drive signal is updated, here the updating is performed on thebasis of the first drive scheme.

The BLDCM is controlled by using the updated PWM drive signal, toperform commutation.

In the above solution, the operation of updating the PWM drive signal,here the updating is performed on the basis of the first drive schemeincludes the following operations.

A duty cycle of the PWM drive signal is updated according to the firstdrive scheme.

A phase of the PWM drive signal is updated.

In the above solution, the operation of updating, according to the firstdrive scheme, the duty cycle of the PWM drive signal includes thefollowing operations.

An operating voltage of each of switching devices in the three-phasefull-bridge circuit is determined by using the first drive scheme.

A duty cycle of a respective PWM drive signal corresponding to each ofthe switching devices is updated by using the determined operatingvoltage of each of the switching devices.

In the above solution, for each of the switching devices in thethree-phase full-bridge circuit, the duty cycle of the PWM drive signalis updated by updating a value of a first register corresponding to theduty cycle of the respective PWM drive signal.

In the above solution, the operation of updating the phase of the PWMdrive signal includes the following operations.

The phase of the PWM drive signal is updated by updating a value of asecond register corresponding to a PWM carrier signal.

In the above solution, the operation of updating, by updating the valueof the second register corresponding to the PWM carrier signal, thephase of the PWM drive signal includes the following operations.

An updated carrier signal is obtained by setting the value of the secondregister to a specific value when it is determined that commutation isto be carried out.

The phase of the PWM drive signal is updated by using the updatedcarrier signal.

In the above solution, the method further includes the followingoperations.

A back electromotive force signal of the BLDCM is acquired.

A back electromotive force zero-crossing point (ZCP) time of the BLDCMis determined according to the acquired back electromotive force signal.

It is determined that the BLDCM is to be commutated when a first timeelapses after the back electromotive force ZCP time.

In the above solution, the operation of determining the first drivescheme, corresponding to the detected position of the rotor, of theBLDCM includes the following operations.

A drive scheme corresponding to the detected position of the rotor isfound in a first mapping table.

The found drive scheme is used as the first drive scheme.

In the above solution, a PWM modulation scheme of the PWM drive signalis H-PWM-L-ON, or H-ON-L-PWM, or ON-PWM, or PWM-ON.

Embodiments of the disclosure further provide a commutation controldevice for a BLDCM, which includes a first determination unit, a seconddetermination unit, an updating unit and a control unit.

The first determination unit is configured to detect a position of arotor in the BLDCM, here the detecting is further configured to betriggered by commutation of the BLDCM.

The second determination unit is configured to determine a first drivescheme, corresponding to the detected position of the rotor, of theBLDCM, here the first drive scheme indicates a manner in which athree-phase full-bridge circuit of the BLDCM operates.

The updating unit is configured to update a PWM drive signal, here theupdating is performed on the basis of the first drive scheme.

The control unit is configured to control the BLDCM by using the updatedPWM drive signal, to perform commutation.

Embodiments of the disclosure further provide a commutation controldevice for a BLDCM. The device includes: a processor, and a memoryconfigured to store computer programs executable on the processor.

The processor is configured to perform operations of any one of theabove methods when executing the computer programs.

Embodiments of the disclosure further provide a storage medium havingstored therein computer programs that, when executed by a processor,causes the processor to implement operations of any one of the abovemethods.

In the commutation control method and device for the BLDCM, and thestorage medium provided by the embodiments of the disclosure, a positionof a rotor in the BLDCM is detected, here the detecting is furtherconfigured to be triggered by commutation of the BLDCM; a first drivescheme, corresponding to the detected position of the rotor, of theBLDCM is determined, here the first drive scheme indicates a manner inwhich a three-phase full-bridge circuit of the BLDCM operates; a PWMdrive signal is updated, here the updating is performed on the basis ofthe first drive scheme; and the BLDCM is controlled by using the updatedPWM drive signal, to perform commutation. In the solutions provided bythe embodiments of the disclosure, when the BLDCM is to be commutated,updating to obtain the PWM drive signal by using the first drive schemeenables a commutation action to take effect immediately, so thattimeliness of commutation for the BLDCM and stability of commutationperiod may be ensured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of driving a three-phase full-bridgecircuit of a BLDCM in the related art.

FIG. 2A is a schematic diagram of an H-PWM-L-ON modulation scheme in therelated art.

FIG. 2B is a schematic diagram of an H-ON-L-PWM modulation scheme in therelated art.

FIG. 2C is a schematic diagram of an ON-PWM modulation scheme in therelated art.

FIG. 2D is a schematic diagram of a PWM-ON modulation scheme in therelated art.

FIG. 3 is a schematic diagram of a carrier signal, an ideal commutationsignal, an actual commutation signal, and respective phase drive signalsin the related art.

FIG. 4 is a schematic flowchart of a commutation control method for aBLDCM according to some embodiments of the disclosure.

FIG. 5 is a schematic structural diagram of some application embodimentsof the disclosure where a BLDCM is applied to a hardware system in anelectronic device.

FIG. 6 is a schematic structural diagram of a commutation control systemfor a BLDCM according to some application embodiments of the disclosure.

FIG. 7 is a schematic diagram of carrier commutation synchronizationupdate, a modulation wave signal, a carrier signal, an ideal commutationsignal, and respective phase drive signals in a process of implementinga commutation control method for a BLDCM according to some applicationembodiments of the disclosure.

FIG. 8 is a schematic flowchart for implementing commutation for a BLDCMaccording to some application embodiments of the disclosure.

FIG. 9 is a schematic structural diagram of composition of a commutationcontrol device for a BLDCM according to some embodiments of thedisclosure.

FIG. 10 is a schematic structural diagram of hardware composition of acommutation control device for a BLDCM according to some embodiments ofthe disclosure.

FIG. 11A is a schematic diagram of a carrier signal, an idealcommutation signal, an actual commutation signal, a terminal voltage anda terminal current without using the solution of some embodiments of thedisclosure.

FIG. 11B is a schematic diagram of a carrier signal, an idealcommutation signal, an actual commutation signal, a terminal voltage anda terminal current by using the solution of some embodiments of thedisclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

In order to make the objective, technical solutions and advantages ofembodiments of the disclosure clearer, specific technical solutions ofthe disclosure are further described in detail below in conjunction withthe accompanying drawings of the embodiments of the disclosure. Thefollowing embodiments are intended to explain the disclosure, but arenot intended to limit the scope of the disclosure.

In the embodiments of the disclosure, the PWM modulation scheme of thePWM drive signal is a modulation scheme suitable for a high-speed BLDCM,such as H-PWM-L-ON, or H-ON-L-PWM, or ON-PWM, or PWM-ON, etc. FIGS. 2A,2B, 2C and 2D show that the above-mentioned H-PWM-L-ON, H-ON-L-PWM,ON-PWM and PWM-ON modulation schemes correspond to drive schemes of sixswitching devices S1 to S6 in a three-phase full-bridge circuit of FIG.1 respectively. In the following descriptions, the PWM modulation schemeof H-PWM-L-ON is taken as an example.

In the related art, a commutation technique of the BLDCM has a problemthat the PWM drive signal cannot control the BLDCM to performcommutation in time under a high-speed condition. The failure of theBLDCM to perform commutation in time further causes a series of negativephenomena, including: commutation delay, commutation unevenness, anddisappearance of back electromotive force ZCP.

Here, the failure to perform commutation in time is shown in FIG. 3. Asshown in FIG. 3, an ideal commutation signal 302 may appear at anyposition of a PWM carrier signal 301, but a PWM state of a PWM drivesignal may be updated only when the PWM carrier signal 301 is at aminimum value (such as zero) or a maximum value (such as a period value)(that is, a state of a switching device corresponding to the PWM drivesignal may be updated only when the amplitude of the PWM carrier signalis at a minimum value or a maximum value). Here, a case where the PWMstate is updated at the zero point is taken as an example, when theideal commutation signal 302 appears, the PWM state cannot be updated intime until the carrier signal 301 has a zero point. Therefore, an actualcommutation signal 303 always lags behind the ideal commutation signal302. Reference numerals 304, 305 and 306 show drive signals of A-phase,B-phase and C-phase, respectively. The failure of the BLDC to performcommutation in time results in the following impacts.

1. Commutation Delay

Since the BLDCM cannot perform commutation in time, the commutationoperation of the BLDCM is delayed to a zero point of the currentcarrier. At this time, commutation for the BLDCM has a maximum delay ofone PWM period. As the rotation speed of the BLDCM increases, a carrierratio (that is, a ratio of a carrier frequency to an operating frequencyof the BLDCM) becomes lower, and the proportion of a delay time (thatis, a ratio of the delay time to the period of the carrier signal)increases. At this time, the current of the BLDCM increases sharply andits efficiency decreases.

2. Commutation Unevenness

Since the BLDCM cannot perform commutation in time, in FIG. 3, theperiod of the actual commutation signal 303 may only be integral timesof the period of the carrier signal 301, and the period of the idealcommutation signal 302 is 2.7 times of the period of the carrier signal301. Therefore, the period of the actual commutation signal 303 may havetwo PWM carrier periods (indicated by 309 and 312) or three PWM periods(indicated by 308, 310, 311 and 313), which causes commutationunevenness. Moreover, when the rotation speed of the BLDCM increases,the actual number of PWM waves per sector decreases, and the phenomenonof commutation unevenness becomes serious. At this time, oscillation ofthe current of the BLDCM becomes larger and the noise becomes larger.

3. Disappearance of ZCP

Since the BLDCM cannot perform commutation in time, freewheeling endtime of the BLDCM is delayed in a short commutation period (such asindicated by 309 and 312 in FIG. 3). At this time, the phenomenon ofdisappearance of a ZCP may occur (here, it may be understood by thoseskilled in the art that under an ideal condition, it is desirable forthe BLDCM to perform commutation when it is at a position such as 0degree, 60 degree, 120 degree, etc., and it is able to detect the ZCPwhen it is at a position such as 30 degree, 90 degree, 150 degree, etc.Assuming that the commutation freewheeling time for the BLDCM isequivalent to the time taken for the BLDCM to rotate 20 degree, thenafter the BLDCM performs commutation when it is at the position of 0degree, the freewheeling ends when it is at the position of 20 degree,and at this time, the ZCP may be detected when it is at the position of30 degree. However, when the BLDCM has a commutation delay, for example,commutation that should be performed when it is at the position of 0degree is delayed to be performed until it is at the position of 15degree, the freewheeling end time will occur when it is at the positionof 35 degree (15 degree+20 degree=35 degree), and at this time, the ZCPcannot be detected when it is at the position of 30 degree, that is, thephenomenon of disappearance of the ZCP occurs), even the sensorlesssolution for the BLDCM becomes unstable.

Based on the above descriptions, in various embodiments of thedisclosure, a position of a rotor in the BLDCM is detected, here thedetecting is further configured to be triggered by commutation of theBLDCM; a first drive scheme, corresponding to the detected position ofthe rotor, of the BLDCM is determined, here the first drive schemeindicates a manner in which a three-phase full-bridge circuit of theBLDCM operates; a PWM drive signal is updated, here the updating isperformed on the basis of the first drive scheme; the BLDCM iscontrolled by using the updated PWM drive signal, to performcommutation, so as to achieve a maximum possibility of timelycommutation.

Embodiments of the disclosure provide a commutation control method for aBLDCM, which includes the following operations as shown in FIG. 4.

In operation S401: a position of a rotor in the BLDCM is detected, herethe detecting is further configured to be triggered by commutation ofthe BLDCM.

In a practical application, the position of the rotor in the BLDCM isfrom 0 degree to 360 degree, and every 60 degree is classified as asector, and there are six sectors in total. Sector I is from 0 degree to60 degree, sector II is from 60 degree to 120 degree, sector III is from120 degree to 180 degree, sector IV is from 180 degree to 240 degree,sector V is from 240 degree to 300 degree, and sector VI is from 300degree to 360 degree (0 degree).

Here, the operation that the detecting is further configured to betriggered by commutation of the BLDCM may be understood as performing acorresponding detection when it is determined that the BLDCM is to becommutated. The time when the BLDCM is to be commutated refers to anideal time for commutating the BLDCM, that is, the time when the rotorin the BLDCM is at the position of 60 degree, or 120 degree, or 180degree, or 240 degree, or 300 degree, or 360 degree (0 degree). At thistime, the specific position of the rotor in the BLDCM is detected todetermine sectors where the BLDCM performs commutation, for example,when 60 degree, or 120 degree, or 180 degree, or 240 degree, or 300degree, or 360 degree (0 degree) is detected, it may be determined thatthe BLDCM is to be commutated. At this time, when it is further detectedthat the rotor in the BLDCM is at the position of 60 degree, it may bedetermined that the BLDCM will commutate from sector Ito sector II.

In a practical application, the position of the rotor in the BLDCM maybe obtained by a sensorless technique, or may be directly read by arotor position sensor (Hall sensor, photoelectric encoder, etc.) in theBLDCM.

In some embodiments, a specific manner of obtaining the position of therotor in the BLDCM by the sensorless technique includes the followingoperations. A back electromotive force signal of the BLDCM is acquired.A back electromotive force ZCP time of the BLDCM is determined accordingto the acquired back electromotive force signal. It is determined thatthe BLDCM is to be commutated when a first time elapses after the backelectromotive force ZCP time.

Here, the first time is the time taken for the position of the rotor inthe BLDCM to be changed by 30 degree. Compared with the manner ofreading the position of the rotor by a sensor, the sensorless techniquethat obtains the position of the rotor in the BLDCM does not need to beadditionally equipped with a sensor and thus reduces hardware cost andincreases the reliability to a certain extent.

In operation S402: a first drive scheme, corresponding to the detectedposition of the rotor, of the BLDCM is determined, here the first drivescheme indicates a manner in which a three-phase full-bridge circuit ofthe BLDCM operates.

Here, in a practical application, the first drive scheme may indicate anideal drive scheme of the three-phase full-bridge circuit of the BLDCM(for example, the drive schemes of six switching devices S1 to S6 in thethree-phase full-bridge circuit corresponding to the H-PWM-L-ONmodulation scheme as shown in FIG. 2A); may also be another optimizeddrive scheme of the three-phase full-bridge circuit of the BLDCM.

In a practical application, after determining sectors where commutationis performed, the first drive scheme may be obtained by finding in amapping table preset in a program, or it may be obtained by anothermanner, which is not limited here.

In some embodiments, the specific manner of obtaining the first drivescheme by finding in the table includes the following operations. Adrive scheme corresponding to the detected position of the rotor isfound in a first mapping table. The found drive scheme is used as thefirst drive scheme.

Here, the first mapping table is a table that has established acorresponding mapping relationship between the position of the rotor inthe BLDCM and the corresponding first drive scheme, and has been storedin advance.

In operation S403: a PWM drive signal is updated, here the updating isperformed on the basis of the first drive scheme.

Here, the PWM drive signal refers to the PWM drive signal acting on thethree-phase full-bridge circuit of the BLDCM. In a practicalapplication, six switching devices in the three-phase full-bridgecircuit correspond to different PWM drive signals respectively, that is,three-phase six-state PWM drive signals. The PWM drive signal of each ofthe switching devices may control the operating state of thecorresponding switching device.

In the related art, the state of the PWM drive signal may be updatedonly when the amplitude of the PWM carrier signal is at a minimum valueor a maximum value, therefore a commutation delay may occur by using thePWM drive signal in the related art. Here, the PWM drive signal isupdated by using the first drive scheme, the updated PWM drive signalenables the commutation action to take effect immediately.

In some embodiments of the disclosure, the operation of updating the PWMdrive signal, here the updating is performed on the basis of the firstdrive scheme includes the following operations.

A duty cycle of the PWM drive signal is updated according to the firstdrive scheme.

A phase of the PWM drive signal is updated.

Here, updating the phase of the PWM drive signal is performed at acertain moment when the BLDCM is to be commutated.

In some embodiments, the operation of updating, according to the firstdrive scheme, the duty cycle of the PWM drive signal includes thefollowing operations.

An operating voltage of each of switching devices in the three-phasefull-bridge circuit is determined by using the first drive scheme.

A duty cycle of a respective PWM drive signal corresponding to each ofthe switching devices is updated by using the determined operatingvoltage of each of the switching devices.

Here, in a practical application, updating the PWM drive signal of theBLDCM is specifically implemented by updating a register in software.

Based on the above descriptions, in some embodiments, for each of theswitching devices in the three-phase full-bridge circuit, the duty cycleof the PWM drive signal is updated by updating a value of a firstregister corresponding to the duty cycle of the respective PWM drivesignal.

In some embodiments, the operation of updating the phase of the PWMdrive signal includes the following operations.

The phase of the PWM drive signal is updated by updating a value of asecond register corresponding to a PWM carrier signal.

In some embodiments, the operation of updating, by updating the value ofthe second register corresponding to the PWM carrier signal, the phaseof the PWM drive signal includes the following operations.

An updated carrier signal is obtained by setting the value of the secondregister to a specific value when it is determined that commutation isto be carried out.

The phase of the PWM drive signal is updated by using the updatedcarrier signal.

Here, the specific value is a maximum value or a minimum value of thesecond register.

In operation S404: the BLDCM is controlled by using the updated PWMdrive signal, to perform commutation.

Here, the updated PWM drive signal may control the operating state (suchas, on or off) of the corresponding switching device to control theBLDCM to perform commutation.

Embodiments of the disclosure provide a commutation control method for aBLDCM, in which a position of a rotor in the BLDCM is detected, here thedetecting is further configured to be triggered by commutation of theBLDCM; a first drive scheme, corresponding to the detected position ofthe rotor, of the BLDCM is determined, here the first drive schemeindicates a manner in which a three-phase full-bridge circuit of theBLDCM operates; a PWM drive signal is updated, here the updating isperformed on the basis of the first drive scheme; and the BLDCM iscontrolled by using the updated PWM drive signal, to performcommutation. In the solution provided by some embodiments of thedisclosure, when the BLDCM is to be commutated, updating to obtain thePWM drive signal by using the first drive scheme enables a commutationaction to take effect immediately, so that timeliness of commutation forthe BLDCM and stability of commutation period may be ensured.

Moreover, the solutions of the embodiments of the disclosure do notrequire improvements in hardware, and implement timely commutation forthe BLDCM only by software, which does not increase the hardware cost,and is simple and convenient to implement.

The disclosure will be described in detail below in conjunction withspecific application examples.

In some application embodiments, the BLDCM has six sectors, and it isimplemented as shown in FIG. 5 where the BLDCM is applied to a hardwaresystem in an electronic device. As shown in FIG. 5, the system includes:a BLDCM 501, a three-phase full-bridge circuit 502, a direct current(DC) bus capacitor 503, a battery 504, a PWM drive signal 505, amicrocontroller unit (MCU) 506, and a back electromotive force detectioncircuit 507.

In a practical application, the MCU 506 may also be a central processingunit (CPU). Here, the MCU 506 is responsible for sampling the backelectromotive force signal of the BLDCM, and controls the three-phasefull-bridge circuit 502 through the drive signal to drive the BLDCM 501.

In some application embodiments, it is implemented as the commutationcontrol system for the BLDCM shown in FIG. 6. As shown in FIG. 6, thecontrol system includes: a BLDCM 501, a three-phase full-bridge circuit502, a PWM module 603, commutation logic 604, a timer 605, a backelectromotive force ZCP detection module 606, and an Analog-to-DigitalConverter (ADC) sampling module 607.

The ADC sampling module 607 samples the back electromotive force signalof the BLDCM, and then the ZCP detection module 606 detects the positionof the ZCP continuously. Once the ZCP is detected, the timer 605 isimmediately activated to delay 30 degree to trigger the commutationsignal. When the commutation signal appears (that is, when it isdetermined that the BLDCM is to be commutated), the duty cycle of thePWM drive signal in the PWM module 603 is updated by finding in thecommutation logic 604 (equivalent to the first mapping table), and theamplitude of the carrier signal in the PWM module 603 is triggered to beupdated. The PWM module 603 obtains an updated PWM drive signalaccording to the updated duty cycle of the PWM drive signal and thecarrier signal. The PWM drive signal acts on the three-phase full-bridgecircuit 502, and finally the BLDCM 501 realizes the purpose of timelycommutation.

In some application embodiments, in order to allow the PWM drive signalto control the BLDCM to perform commutation in time, the drive schemeindicated in the PWM drive signal is checked and determined to becorrect, and then the PWM drive signal is used to control the BLDCM toperform commutation at the correct time.

Here, the duty cycle of the PWM drive signal directly reflects theamplitude of the PWM drive signal, and is used to control a manner inwhich the switching devices in the three-phase full-bridge circuitoperate.

Regarding the implementation of updating the duty cycle of the PWM drivesignal, in some practical applications, a commutation logic table(equivalent to the first mapping table) is configured and stored in theMCU 506 in advance. In some application embodiments of the disclosure,the commutation logic table is shown in Table 1, the position of therotor in the BLDCM is from 0 degree to 360 degree, every 60 degree isclassified as a sector; the driver outputs the corresponding drivescheme in each sector. In the drive scheme in Table 1, A, B, and Crepresent A-phase, B-phase and C-phase of the BLDCM respectively; + and− represent an upper switching device and a lower switching device ofeach of the phases respectively.

TABLE 1 Rotor Position 0°~60° 60°~120° 120°~180° 180°~240° 240°~300°300°~360° Sector I II III IV V VI Drive scheme A + B− A + C− B + C− B +A− C + A− C + B−

Here, the H-PWM-L-ON modulation scheme in FIG. 2A is taken as anexample, there are three states of each of the switching devices in FIG.2A: a PWM state (corresponding to the segment of the square wave in S1,S3 and S5 in FIG. 2A), an all-on state (corresponding to the segment ofthe square wave in S2, S4 and S6 in FIG. 2A), an off state(corresponding to the segment without the square wave in S1 to S6 inFIG. 2A), here the three states directly reflect the operating voltageacting on each of the switching devices.

Here, Table 1, FIG. 1 and FIG. 2 are combined together to illustrate thespecific implementation of updating the duty cycle of the PWM drivesignal.

FIRST EXAMPLE Commutation From Sector VI to Sector I is Taken as anExample

When it is determined that the BLDCM is to be commutated, and it isdetected that the rotor in the BLDCM is at the position of 0 degree, andthe drive scheme corresponding to the position of 0 degree where therotor in the BLDCM is located is found from Table 1; the found drivescheme A+B− is used as the first drive scheme, that is, the upperswitching device S1 of A-phase and the lower switching device S4 ofB-phase in FIG. 1 is turned on at this time, and the remaining fourdevices S2, S3, S5, S6 are turned off; the operating voltage of each ofthe switching devices in the three-phase full-bridge circuit is obtainedin conjunction with FIG. 2A, that is, the upper switching device S1 ofA-phase is in the PWM state, the lower switching device S4 of B-phase isin the all-on state, and each of the remaining switching devices S2, S3,S5, S6 is in the off state. At this time, the register corresponding tothe upper switching device S1 of A-phase is loaded with M (such as avalue between 0 and 1); the register corresponding to the lowerswitching device S4 of B-phase is loaded with a maximum value (such as1); each of four registers corresponding to the remaining four devicesS2, S3, S5, S6 is loaded with a minimum value (such as 0).

SECOND EXAMPLE Commutation From Sector I to Sector II is Taken as anExample

When it is determined that the BLDCM is to be commutated, and it isdetected that the rotor in the BLDCM is at the position of 60 degree,and the drive scheme corresponding to the position of 60 degree wherethe rotor in the BLDCM is located is found from Table 1; the found drivescheme A+C− is used as the first drive scheme, that is, the upperswitching device S1 of A-phase and the lower switching device S6 ofC-phase in FIG. 1 is to be turned on at this time, and the remainingfour devices S2, S3, S4, S5 are turned off; the operating voltage ofeach of the switching devices in the three-phase full-bridge circuit isobtained in conjunction with FIG. 2A, that is, the upper switchingdevice S1 of A-phase is in the PWM state, the lower switching device S6of C-phase is in the all-on state, and each of the remaining switchingdevices S2, S3, S4, S5 is in the off state. At this time, the registercorresponding to the upper switching device S1 of A-phase is loaded withM (such as a value between 0 and 1); the register corresponding to thelower switching device S6 of C-phase is loaded with a maximum value(such as 1); each of four registers corresponding to the remaining fourdevices S2, S3, S4, S5 is loaded with a minimum value (such as 0).

It should be noted that in the process of implementing the digital PWMtechnique, the duty cycle of the PWM drive signal corresponding to eachof the switching devices corresponds to the operating voltage of each ofthe switching devices after a series of conversion calculations in theprocessor.

The register corresponding to each of the switching devices in FirstExample and Second Example is the first register, and the duty cycle ofthe PWM drive signal is updated here.

Regarding the implementation of updating the phase of the PWM drivesignal, in some practical applications, an initial configuration of thePWM module 602 in the MCU 506 is provided in advance. The main functionof the PWM module 602 is to generate the PWM drive signal according tothe PWM modulation wave signal (here, the PWM modulation wave signal andthe duty cycle of the PWM drive signal are the same concept) and the PWMcarrier signal. In some application embodiments of the disclosure, thefollowing settings are made in the initial configuration of the PWMmodule 602.

1. The carrier in the carrier signal adopts a monotonically increasingwave (for example, a saw-tooth wave).

2. At a zero point of the carrier signal, the PWM drive signal starts tooutput a high level.

3. When the carrier signal is equal to the modulation wave signal, thePWM drive signal starts to output a low level.

4. The value of the first register of each of the switching devices isupdated at the zero point of the carrier (that is, the state, such asthe PWM state, the all-on state and the off state, of each of theswitching devices are updated).

FIG. 7 shows a schematic diagram of carrier commutation synchronizationupdate. A carrier commutation synchronization update signal 701, a PWMmodulation wave signal 702, a PWM carrier signal 703, an idealcommutation signal 704, an A-phase drive signal 705, a B-phase drivesignal 706 and a C-phase drive signal 707 are included. In FIG. 7,according to the above-mentioned initial configuration rule of the PWMmodule 602, the PWM drive signal is generated from the PWM modulationwave signal 702 and the PWM carrier signal 703.

Here, when it is determined that the BLDCM is to be commutated, that is,when the ideal commutation signal 704 appears, the carrier commutationsynchronization signal 701 is synchronously generated to forcibly updatethe amplitude of the PWM carrier signal 703. Here, forcibly updating theamplitude of the PWM carrier signal 703 may be specifically implementedby forcibly setting the value of the register corresponding to the PWMcarrier signal. During specific implementation, the value of theregister corresponding to the PWM carrier signal may be set to aspecific value when it is determined that the commutation is to becarried out, where the specific value is a maximum value (such as theperiod value) or a minimum value (such as zero). In some applicationembodiments, the value of the register corresponding to the PWM carriersignal is set to zero. Since the state of each of the switching devicesis updated at the zero point of the PWM carrier signal 703, after theamplitude of the PWM carrier signal 703 is forcibly updated insynchronization, the phase of the PWM drive signal will be changedimmediately. This eliminates the problem that the carrier signal and thecommutation signal are not synchronized.

It should be noted that in the process of implementing the digital PWMtechnique, the register corresponding to the PWM carrier signal isimplemented in the form of a counter, that is, the PWM carrier signalcounts from 0 to a period value in sequence according to a presetperiod, and then starts counting from 0 to the period value again afterreaching the period value, and the cycle repeats in such way. In someapplication embodiments, the value of the register corresponding to thePWM carrier signal is directly set to 0 when it is determined that thecommutation is to be carried out, and then the PWM carrier signal startscounting from 0 to the period value, and that cycle repeats in such way,which is shown as follows in FIG. 7: the saw-tooth wave in the PWMcarrier signal 703 has a small saw-tooth wave after two large saw-toothwaves, when the value in the register is forcibly set to zero.

The register corresponding to the PWM carrier signal corresponding toeach of the switching devices is the second register, where the phase ofthe PWM drive signal is updated.

FIG. 8 is a flowchart of a process for implementing commutation for aBLDCM according to some application embodiments. As shown in FIG. 8, theflow includes the following operations.

(1) A commutation signal is detected and an interrupt is executed.

Here, when the commutation signal is detected, it is determined that theBLDCM is to be commutated, and the position of the rotor is furtherdetermined simultaneously.

(2) A commutation logic table is found.

According to the determined position of the rotor, the correspondingfirst drive scheme is found in the commutation logic table.

(3) A duty cycle register of a PWM signal is loaded.

Here, the operating voltage of each of the switching devices in thethree-phase full-bridge circuit is determined according to thedetermined first drive scheme, and the operating voltage of each of theswitching devices is used to load the amplitude of the modulation wavecorresponding to each of the switching devices (as mentioned above, herethe amplitude of the modulation wave and the PWM duty cycle are the sameconcept).

(4) A register of a PWM carrier signal is loaded.

Here, the value of the register of the PWM carrier signal correspondingto each of the switching devices is set to 0 when it is determined thatcommutation is to be carried out, here the phase of the PWM drive signalis updated immediately (that is, the state of each of the switchingdevices is updated instantly) when the PWM carrier signal is a minimumvalue. At the same time, the updated PWM drive signal is obtained.

(5) Commutation is performed.

A commutation operation is performed according to the updated PWM drivesignal is performed.

(6) The interrupt is exited.

The above operations (1) to (6) are repeatedly performed to achieve atimely commutation for the BLDCM.

It may be seen from the above descriptions that in the embodiments ofthe disclosure, under the premise of ensuring the correct drive scheme,the amplitude of the PWM carrier signal is forcibly set to a minimumvalue when the BLDCM is to be commutated, which enables the state of thePWM drive signal to be updated immediately so that the BLDCM performscommutation timely, thereby ensuring the timeliness of commutation forthe BLDCM and stability of commutation period, breaking inherent limitsof the PWM update mechanism.

On the other hand, as shown in FIG. 11A and FIG. 11B, under thecondition that the solutions of the embodiments of the disclosure areused, the waveform of the actual commutation signal is uniform andcloser to the ideal commutation signal, and the situation that ZCPdisappears in the process of detecting the terminal voltage is avoided,and the oscillation amplitude of the terminal current is smaller. Thatis, the embodiments of the disclosure ensure stability of commutationperiod so that the freewheeling end time is relatively stable when thePWM state changes, thereby ensuring the possibility of detecting ZCP,meanwhile alleviating problems such as current oscillation for theBLDCM, reduction of working efficiency, increased noise, and instabilityof controlling the BLDCM, and the like.

In order to implement the method according to the embodiments of thedisclosure, the embodiments of the disclosure further provide acommutation control device for a BLDCM, and FIG. 9 is a schematicstructural diagram of a composition of an device according to someembodiments of the disclosure, as shown in FIG. 9, the device 900includes: a first determination unit 901, a second determination unit902, an updating unit 903 and a control unit 904.

The first determination unit 901 is configured to detect a position of arotor in the BLDCM, here the detecting is further configured to betriggered by commutation of the BLDCM.

The second determination unit 902 is configured to determine a firstdrive scheme, corresponding to the detected position of the rotor, ofthe BLDCM, here the first drive scheme indicates a manner in which athree-phase full-bridge circuit of the BLDCM operates.

The updating unit 903 is configured to update a PWM drive signal on thebasis of the determined first drive scheme.

The control unit 904 is configured to control the BLDCM by using theupdated PWM drive signal, to perform commutation.

In some embodiments, the updating unit 903 includes a first updatingmodule and a second updating module.

The first updating module is configured to update, according to thefirst drive scheme, a duty cycle of the PWM drive signal.

The second updating module is configured to update a phase of the PWMdrive signal.

In some embodiments, the first updating module is configured to:determine, by using the first drive scheme, an operating voltage of eachof switching devices in the three-phase full-bridge circuit; and

update, by using the determined operating voltage of each of theswitching devices, a duty cycle of a respective PWM drive signalcorresponding to each of the switching devices.

In some embodiments, the first updating module is configured to: foreach of the switching devices in the three-phase full-bridge circuit,update the duty cycle of the PWM drive signal by updating a value of afirst register corresponding to the duty cycle of the respective PWMdrive signal.

In some embodiments, the second updating module is configured to updatethe phase of the PWM drive signal by updating a value of a secondregister corresponding to a PWM carrier signal.

In some embodiments, the second updating module is configured to: obtainan updated carrier signal by setting the value of the second register toa specific value when it is determined that commutation is t to becarried out; and

update, by using the updated carrier signal, the phase of the PWM drivesignal.

In some embodiments, the first determination unit 901 is configured to:acquire a back electromotive force signal of the BLDCM; determine,according to the acquired back electromotive force signal, a backelectromotive force ZCP time of the BLDCM; and determine, when a firsttime elapses after the back electromotive force ZCP time, that the BLDCMis to be commutated.

In some embodiments, the second determination unit 902 is configured to:find, in a first mapping table, a drive scheme corresponding to thedetected position of the rotor;

use the found drive scheme as the first drive scheme.

In some embodiments, a PWM modulation scheme of the PWM drive signal isH-PWM-L-ON, or H-ON-L-PWM, or ON-PWM, or PWM-ON.

In some practical applications, the first determination unit 901, thesecond determination unit 902, the updating unit 903 and the controlunit 904 may be implemented by a processor in the commutation controldevice for the BLDCM.

It should be noted that when performing the control of commutation forthe BLDCM, the commutation control device for the BLDCM provided by theabove embodiments only uses the division of the above-mentioned programmodules as an illustrative example. In a practical application, theabove process allocation may be completed by different program modulesas needed, that is, the internal structure of the device is divided intodifferent program modules to complete all or part of the above-mentionedprocesses. Moreover, the embodiments of the commutation control devicefor the BLDCM and of the commutation control method for the BLDCMprovided in the above embodiments belong to the same concept, and thespecific implementation thereof may refer to the method embodiments forthe details, which will not be repeated here.

Based on the hardware implementation of the above-mentioned programmodules, and in order to implement the method according to theembodiments of the disclosure, the embodiments of the disclosure providea device for determining a back electromotive force ZCP threshold for aBLDCM. As shown in FIG. 10, the device 1000 includes a processor 1001,and a memory 1002 configured to store computer programs executable onthe processor.

The processor 1001 is configured to execute the method provided by oneor more of the above-mentioned technical solutions when executing thecomputer programs.

In a practical application, as shown in FIG. 10, the components of thedevice 1000 are coupled together by a bus system 1003. It may beappreciated that the bus system 1003 is configured to implementconnection and communication among these components. The bus system 1003includes, in addition to data bus, power bus, control bus, and statussignal bus. For clarity, however, various buses are labeled as the bussystem 1003 in FIG. 10.

In some exemplary embodiments, the embodiments of the disclosure furtherprovide a storage medium, which is a computer-readable storage medium,such as a memory 1002 including computer programs executable by theprocessor 1001 of the a device 1000 for determining a back electromotiveforce ZCP threshold for a BLDCM, to perform operations described in theforegoing methods. The computer-readable storage medium may beFerromagnetic Random Access Memory (FRAM), Read Only Memory (ROM),Programmable Read-Only Memory (PROM), Erasable Programmable Read-OnlyMemory (EPROM), Electrically Erasable Programmable Read-Only Memory(EEPROM), Flash Memory, magnetic surface memory, optical disk, or memorysuch as Compact Disc Read-Only Memory (CD-ROM), etc.

It should be noted that the terms “first”, “second” or the like are usedto distinguish among similar objects, rather than describing a specificorder or sequence.

In addition, the technical solutions described in the embodiments of thedisclosure may be combined arbitrarily without conflict.

The foregoing descriptions are merely illustrative of the preferredembodiments of the disclosure and are not intended to limit theprotection scope of the disclosure.

1. A commutation control method for a Brush Less Direct Current Motor(BLDCM), comprising: detecting a position of a rotor in the BLDCM,wherein the detecting is further configured to be triggered bycommutation of the BLDCM; determining a first drive scheme,corresponding to the detected position of the rotor of the BLDCM,wherein the first drive scheme indicates a manner in which a three-phasefull-bridge circuit of the BLDCM operates; updating a Pulse WidthModulation (PWM) drive signal, wherein the updating is performed basedon the first drive scheme; and controlling the BLDCM by using theupdated PWM drive signal, to perform commutation.
 2. The method of claim1, wherein the updating the PWM drive signal, wherein the updating isperformed based on the first drive scheme comprises: updating, accordingto the first drive scheme, a duty cycle of the PWM drive signal; andupdating a phase of the PWM drive signal.
 3. The method of claim 2,wherein the updating, according to the first drive scheme, the dutycycle of the PWM drive signal comprises: determining, by using the firstdrive scheme, an operating voltage of each of switching devices in thethree-phase full-bridge circuit; and updating, by using the determinedoperating voltage of each of the switching devices, a duty cycle of arespective PWM drive signal corresponding to each of the switchingdevices.
 4. The method of claim 3, wherein for each of the switchingdevices in the three-phase full-bridge circuit, the duty cycle of thePWM drive signal is updated by updating a value of a first registercorresponding to the duty cycle of the respective PWM drive signal. 5.The method of claim 2, wherein the updating the phase of the PWM drivesignal comprises: updating, by updating a value of a second registercorresponding to a PWM carrier signal, the phase of the PWM drivesignal.
 6. The method of claim 5, wherein the updating, by updating thevalue of the second register corresponding to the PWM carrier signal,the phase of the PWM drive signal comprises: obtaining an updatedcarrier signal by setting the value of the second register to a specificvalue when it is determined that commutation is to be carried out; andupdating, by using the updated carrier signal, the phase of the PWMdrive signal.
 7. The method of claim 1, further comprising: acquiring aback electromotive force signal of the BLDCM; determining, according tothe acquired back electromotive force signal, a back electromotive forcezero-crossing point (ZCP) time of the BLDCM; and determining, when afirst time elapses after the back electromotive force ZCP time, that theBLDCM is to be commutated.
 8. The method of claim 1, wherein thedetermining the first drive scheme, corresponding to the detectedposition of the rotor, of the BLDCM comprises: finding, in a firstmapping table, a drive scheme corresponding to the detected position ofthe rotor; and using the found drive scheme as the first drive scheme.9. The method of claim 1, wherein a PWM modulation scheme of the PWMdrive signal is H-PWM-L-ON, or H-ON-L-PWM, or ON-PWM, or PWM-ON.
 10. Acommutation control device for a Brush Less Direct Current Motor(BLDCM), comprising: a first determination unit, configured to detect aposition of a rotor in the BLDCM, wherein the detecting is furtherconfigured to be triggered by commutation of the BLDCM; a seconddetermination unit, configured to determine a first drive scheme,corresponding to the detected position of the rotor, of the BLDCM,wherein the first drive scheme indicates a manner in which a three-phasefull-bridge circuit of the BLDCM operates; an updating unit, configuredto update a Pulse Width Modulation (PWM) drive signal, wherein theupdating is performed based on the first drive scheme; and a controlunit, configured to control the BLDCM by using the updated PWM drivesignal, to perform commutation.
 11. A commutation control device for aBrush Less Direct Current Motor (BLDCM), comprising: a processor, and amemory configured to store computer programs executable on theprocessor; wherein the processor is configured to perform operations ofthe method of claim 1 when executing the computer programs.
 12. Astorage medium, having stored therein computer programs that, whenexecuted by a processor, causes the processor to implement operations ofthe method of claim 1.